Refractory products and their manufacture



Patented Oct. 5, 1926.

FBEDERIG CHARLES FRIDTJOF LE COULTRE, or MARSEILLE, FRANCE, AssIGNoR r0 SOCIETE' DETUDE DES AGGLoMnREs, or PARIS, FRANCE.

REFRACTORY PRODUCTS AND THEIR MANUFACTURE.

No Drawing. Application filed October 9, 1924, Serial No. 742,723, and in France October 17, 1923.

Processes actually known and used for the manufacture of ultra-refractory products by agglomerating zirconiferous ores, these latter being either in the state of mixtures or in the state of compounds, processes in which use is made of a certain quantity of binders such as gum or lime, kaolin. and also clay, only give poor results as a rule.

The present invention which is a commercial application of the scientific researches of Messieurs Karl and F. Le Coultre, has for its subject a new process for the manufacture of ultra-refractory products by agglomerating zirconiferous ores of all kinds.

This process, which is described hereinafter, gives absolutely remarkable results. The invention more particularly consists in the followingv improvements 1. A special preparation of the ores used, this preparation consisting in heating these ores to a very high temperature in an electric furnace with a circular enclosure and on their discharge from the furnace precipitating them into a strong current of cold water acidulated with 1/1000 sulphuric acid.

2. A suitable composition of the mixture of the powder of the ore and binders, adapted to form a paste with which the products or objects to be manufactured are formed, the said mixture including, besides the powder of the ore to be agglomerated, a binder of an organic nature such as dextrin, tar or the like, adapted to impart to the products the necessary consistency for the first operation between ordinary temperature and 180 0., and a volatile inorganic binder, such as an acid, for example, boric acid or phosphorating acid, or a mineral salt, this second binder being capable of withstanding the temperature necessary to enable the refractory elements to effect their autoagglomeration by the superficial fusion of the particles of the material of which they are formed, the two said binders being hi troduced in proportions according to the nature of the binders used, for example for 100 kgs. of material to be treated 0.5.kg. dextrin and 0.25 kg. boric acid.

3. A method of drying and heating consisting after'the first drying in the mould at ordinary temperature, of a second drying N after removal from the mould, this second drying being effect ed at temperatures which gradually increase up to 180 C. and then baking at a much higher temperature.

These various improvements may be combined, either together or separately, with different known treatments, but the process which gives the best results and which forms the subject of the present invention is the following The zirconiferous ore is crushed into grain then agglomerated summarily under pressure with a suitable organic binder, in the form of cylindrical rods.

These rods are passed continuously through a tunnel furnace with a circular enclosure in which they are heated to a very high temperature. When leaving the furnace the mineral is caused to fall into a strong stream of cold water acidulated with 1/1000 sulphuric acid; The ore is exhausted and abandons a portion of the elements which are deleterious to its refractory qualities. It is then pulverised and the pulverised product is classified in powders of different slzes.

According to the size of the object to be manufactured there are mixed together suitable quantities of the different powders, this mixture being then mixed with boric acid and dextrin in the following proportions: 100.0 kgs. of material, 0.5 kg. dextrin, 0.25 kg. boric acid. These substances are thoroughly mixed together until a perfectly homogeneous mixture is obtained. I

The mouldingmay be effected either by vibration or by pressure.

If this operation is effected by vibration there is added and mixed with the pulverulent mixture previously prepared a quantity of water necessary to form a thickpaste.

The paste obtained is poured into moulds of wood or polished metal, having the shape of the objects to be moulded. The moulds are then placed on a vibrating table until the air-holes contained in the paste have been completely removed.

If the moulding is to be effected under pressure the previously prepared mixture is used in a dry state.

The special moulds for the purpose are filled with the mixture and then subjected to a very high pressure.

After the moulding has been effected either by vibration or by pressure the moulds are placed into a dryer where they remain for the necessary time (variable according to the dimensions) until the articles which they contain have acquired the necessary resistance to enable them to be removed.

After removal from the moulds the drying of the articles is completed by subjecting them to a temperature which gradually increases up to 180 C.

Finally, the articles are placed into a furnace and baked at a much higher temperature. In this manner there are obtained products or objects which are extremely refractory and are capable of resisting a temperature up to 2400 C. and also capable of withstanding a compression of 590 kgs. per

square centimeter and a pulling force of 104C kgs. per square centimeter.

Having thus described my invention, What I claimvas new and desire to secure by Lett-ers Patent is A process for the production of refractory products from zirconiferous ores, consisting in heating the ores to a very high temperature in an electric furnace with a circular enclosure, and in precipitating said ores when they leave the furnace into a violent stream of cold water acidulated with 1/1000 sulphuric acid.

Dated this 20th day of September, 1924.

FREDERIC CHARLES FRIDTJOF le COULTRE. 

